How can I write formatted (i.e. bold, italic, change font size, etc.) text to a file?

[Pedroski55]

If you are happy with PDFs, you can use reportlab and have absolute and minute control over every aspect of formatting.

Read the reportlab_userguide.pdf, especially from page 72.

Here a small example of the almost endless possibilities:

from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import A4
from reportlab.lib.colors import pink, green, brown, white, black
from reportlab.lib.styles import ParagraphStyle
from reportlab.lib.styles import getSampleStyleSheet

path2sizes_pdf = 'reportlab/pdfs/text_sizes.pdf'
stylesheet=getSampleStyleSheet()

c = canvas.Canvas(path2sizes_pdf, pagesize=A4)

def fonts(canvas):
    from reportlab.lib.units import inch
    text = "Now is the time for all good men to..."
    x = 3 * inch
    y = 8 * inch
    size = 13
    for font in canvas.getAvailableFonts():
        canvas.setFont(font, size)
        canvas.drawString(x,y,text)
        canvas.setFont("Helvetica", size)
        canvas.drawRightString(x,y, font+":")
        y = y-size
        size = size + 1

fonts(c)
c.showPage() # closes the page, can't add more to this page
c.save()

path2colour_pdf = 'reportlab/pdfs/text_colours.pdf'
mycolours = [pink, green, brown, white, black]

def colours(canvas):
    from reportlab.lib.units import inch
    text = "Now is the time for all good men to..."
    x = 2 * inch
    y = 8 * inch
    for colour in mycolours:
        canvas.setFont("Helvetica", 14)
        c.setFillColor(colour)
        canvas.drawString(x,y,text)
        y = y-15

colours(c)
c.showPage() # closes the page, can't add more to this page
c.save()    

You can direct reportlab to any font you like and then use that font.

from reportlab.pdfbase import pdfmetrics

# important for getting a Chinese ttf
fontpath = '/home/pedro/.local/share/fonts/'
ttfFile = os.path.join(fontpath, '萌萌哒情根深种-中文.ttf')
pdfmetrics.registerFont(TTFont("Chinese", ttfFile))